Patent GB-1261317-A (GB)
Title: Improvements in fuel cells and fuel cell batteries operating at high temperature
IPC: H01M8/02
Filed: 1970-05-15
Abstract: 1,261,317. Solid-electrolyte fuel cell. COMPAGNIE GENERALE D'ELECTRICITE. 15 May, 1970 [16 May, 1969; 16 Oct., 1969], No. 23779/70. Heading H1B. In a battery of solid electrolyte fuel cells, each cell comprises a tubular section of solid electrolyte material coated inside and out with conductive electrode materials 3, 4, all the tubular sections being parts of the same tube 2; the electrodes inside the tube being staggered relative to those outside so that each inner electrode overlaps the outer one of the next cell and all the cells being connected in series by connecting each overlapping pair of electrodes in the region of overlap. The tube of electrolyte material may be formed by electrolytic deposition on a mandrel. A mixture of zirconium dioxide and yttrium oxide is suspended in a solvent, e.g. nitromethane containing benzoic acid or an acetone-ethanol mixture containing nitrocellulose, the mandrel immersed in the suspension and a potential applied between the mandrel and the liquid container. The tube so formed may be dried, compacted, removed from the mandrel and sintered. During the compacting step, the tube may be wrapped in aluminium foil or polyethylene terephthalate film coated with aluminium to prevent it sticking. Holes for the electrode connections may be made at this stage or later, and filled with silver-palladium alloy. In order to strengthen the connections the holes may be lined with glass by applying a mixture of ground glass and an organic binder and firing it or ground glass may be mixed with the alloy. Alternatively the electrode connections may be made by forming the tube with annular porous sections which are subsequently filled with conductive material. The tube is first formed as a series of spaced non-porous sections either by coating the mandrel with bands of non-conductive material to prevent electrophoretic coating taking place in the spaces or by forming a complete tube and cutting out the spaces. The spaces are then filled with a mixture of solid electrolyte and a pore-forming agent and the tube dried, compacted, removed from the mandrel and pre-sintered to activate the pore-forming agent. The pore-forming agent may be ammonium carbonate or carbamate or graphite. The pores are then filled with a metal salt solution which is then decomposed to give the metal during the final sintering step. The metal salt solution may be produced by dissolving silver-palladium alloy in nitric acid and adding ammonia to a pH of 4. The impregnation and sintering steps may be repeated several times. Before the electrodes are applied to the tube it may be roughened either by treatment with concentrated H 2 SO 4  or by depositing on its surfaces a layer of porous electrolyte material. The inner fuel electrodes may be iron, nickel, cobalt or chromium and the outer oxidant electrodes silver-palladium alloy, indium oxide doped with gallium oxide, antimony or tin. At each end of the battery, the surface of the tube may be coated with metal 10 to provide a terminal. A multiple battery may comprise layers of the batteries all parallel to each other, all the batteries in each layer being connected in parallel by corrugated metal strips 14 and a layer of heat in solution 15 being sandwiched between each two adjacent battery layers.